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120

FERTILISERS  (GENERAL METHODS)

nected with a wash-bottle containing cone, sulphuric acid and the other
with a bulb-tube charged with 20 or 25 c.c. N/io-sulplmric acid. The oven
is heated at 100 and during the drying a slow current of air is passed through
the glass tube. The boat is finally reweighed and the loss of weight dimin-
ished by the weight of ammonium carbonate corresponding with the ammonia
absorbed by N/io-sulphuric acid.

If the fertiliser has an acid reaction and it is feared that loss of volatile
acid or changes rendering the estimation inaccurate will occur in drying,
the fertiliser is first neutralised. To this end 5 grains are weighed in a
weighing bottle, tared together with a thin glass rod. 'flu- mass is then
moistened and neutralised with N-caustic soda, solution. That neutralisa-
tion is approaching is indicated by the ready clarification of the supernatant
liquid and the exact point determined by touching litmus paper with the
rod. The liquid is then evaporated to dryness and the (-rust broken with
the rod, drying being then continued for a further period of .(. hours. Each
c.c. of N-caustie soda, added increases the weight of the dry matter by 0-022
gram.

3. Determination of the Nitrogen

The nitrogen is determined in different ways aecording to its condition,
A. Ammoniacal Nitrogen.-5-10 grams of the substance are mixed
with water (acidified in the ca.se of an alkaline reaction) in a mortar, the
liquid being decanted into a 250 c.c, or 500 c.c. Jlask. The insoluble matter
is washed by decantation and the total liquid ma.de up to volume and the
ammonia in an aliquot part found by distillation with, excess of sodium

hydroxide (or calcined magnesia,, in ca.sc1.
organic nitrogen readily decomposable by
alkali is present). The apparatus and pro-
cedure are described under Kjeldahl method
(see later, (.').

/>'. Nitric Nitrogen. This may be
determined by the two following methods:
i. SCIIUL/K AN-i) TIKMANN'S METHOD.
To a lla.sk a of 150 ,;oo c.c,. rapacity (see
Fig, 2) is fitted a doubly -bored stopper
traversed by two rapillary tubes, one of
which serves lor the delivery of the nitric
oxide into the graduated tube / standing
over water, while the other, slightly con-
stricted at the end, dips into a conical beaker / ; in each tube is inserted a
piece of pressure rubber tubing 5 cm. long fitted with a, screw clip, /, g.

The Ilask is charged with ao c.c. of H>5 % pure sodium nitrate solution
(or 20 c.c. of 2-0% potassium nitrate solution) when the fertiliser contains
sodium (or potassium) nitrate, and about. 30 c.c. of water. The stopper
is inserted and, the two clips being open, the liquid boiled to expel all air
from the flask and the capillary tubes. When the liquid is reduced to a
small volume (about 15 c.c,.), the delivery tube for the nitric oxide is dipped
ir.to a boiled 10% caustic soda solution and the clip closed. If the air has

I =00

th 92% alcohol., 20-30% as good, 15-20% as ordinary, and less than 15% as poor.